JPH07318598A - Measuring method of rf pulse frequency - Google Patents

Abstract

PURPOSE: To enable the frequency of RF pulses to be measured at an RF signal frequency with high precision by computing the RF pulse stream frequency by adding an intermediate pulse stream frequency and a control frequency. CONSTITUTION: An input signal generated by an unit under test UUT device is converted to a pulse stream of a low frequency having an intermediate frequency IF. A mixer 22 receives as input a test signal from a signal supply source 20 and a control frequency generated from a local oscillator 24 and outputs an IF signal as a difference between those frequencies. The IF signal is passed through a BPF26 so as to eliminate undesirable high frequency component. The IF signal is subjected to sampling by means of a digitizer 28, transferred to a signal processor 30 and subjected to frequency analysis. The desirable frequency of the IF signal is about 20 to 30% of a digitized sampling frequency. It is desirable that an least two cycles of the IF signal passed a down converter under the sampling frequency of a selected digitizer exist inside of each captured pulse of test signal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to RF signals, especially pulse R.
It relates to a method for simply measuring the RF carrier frequency of an F signal stream substantially in real time.

[0002]

2. Description of the Related Art Generally, radar / electronic counter measurement (EC
M) In systems, pulsed RF signals of narrow pulse width and low duty cycle are usually used. A pulse of this kind is usually generated by switching a continuous RF source on and off, for example using a pin-switch diode, the duration of which this pulse is very short, for example 100
Can be nanoseconds. The frequency of the RF signal emitted by these systems is an important characteristic for the evaluation of system performance and needs to be measured accurately.

In the conventional RF frequency measuring method, expensive devices such as an electronic counter, a spectrum analyzer, a synchronous detector, and a digital frequency discriminator are used. R
A more specific example of an apparatus currently used for F pulse frequency measurement is a microwave counter EIP 1230A 12 manufactured by EIP Microwave Company.
31A and a hybrid card electronic counter. On the other hand, these methods have a problem that it is impossible to obtain a predetermined frequency measurement accuracy for the latest laser and ECM systems. The accuracy of the electronic counter is low with respect to the pulse width signal of 100 nanoseconds, and the accuracy is only 500 Khz. In addition, electronic counters and spectrum analyzers are expensive, bulky and require specialized hardware. Also, the synchronous detector is limited to a measurement accuracy of 10 Khz unit for a 100 nanosecond pulse width signal, while the digital frequency discriminator can only obtain a measurement accuracy of 100 Khz unit for a 100 nanosecond pulse width signal. On the other hand, as laser and ECM systems are more advanced, test technology also needs to be improved to ensure good system performance.

Furthermore, in order to characterize the performance of the unit under test device (UUT device) in an end-to-end test environment, it does not reach the configuration for accessing the internal structure of the UUT device.

[0005]

The present invention overcomes the above-mentioned problems and can measure the frequency of the RF pulse up to a width of 100 nanoseconds with an extremely high accuracy (30 kHz or less) at an RF signal frequency of up to 40 GHz. The purpose is to provide a real-time method.

[0006]

According to the present invention, the object is (a) an intermediate pulse flow having an intermediate frequency by taking the difference between the control frequency lower than the frequency of the RF pulse flow and the frequency of the RF pulse flow. A step of converting the RF pulse into a laser beam;
(C) extracting pulse points and baseline data from the intermediate pulse stream as samples, and (d) subtracting baseline data from each of the pulse points,
(E) a step of determining a crossing point by using a signal interpolation method for the data obtained in the step (d), and (f)
Calculating the period of the intermediate pulse stream signal from the determined zero-crossing point; (g) calculating the frequency of the intermediate pulse stream signal from the calculated period; and (h) the calculated intermediate pulse stream frequency. And calculating the RF pulse flow frequency by adding the control frequency and the control frequency.

[0007]

In the present invention, however, the RF signal can be mixed with a control frequency, filtered, and then digitized. Also, data from 200 pulses can be sequentially collected, mixed and digitalized to improve frequency calculation accuracy. Next, in the measurement algorithm, the pulse point and the baseline are extracted, the direct current component is removed by subtracting the baseline from the pulse point, the pulse point is zero-interpolated and frequency analysis is performed, and the frequency domain is filtered and the second processing is performed. Can be applied to digitalized data including performing frequency analysis of Moreover, the zero-crossing point can be calculated using any of a number of interpolation methods including the following linear interpolation, Sin (X) X interpolation, and polygonal interpolation, the period of the waveform is calculated, and the frequency is calculated from the calculated result. It can be calculated well.

Also, the Sin of the pulse point and the baseline
The (X) X interpolation method can be used to determine the zero-crossing point and the iterative search algorithm can determine the zero-crossing point with any precision between about 1/100 and about 1 / 1,000,000. . Moreover, the period of the waveform can be calculated, and the frequency can be calculated from the calculation result.

Further in accordance with the present invention, R is substantially real-time using only the RF output of the system under test as input.
The F pulse frequency can be measured with high accuracy. Further, it is possible to realize accurate RF pulse frequency measurement by using a commercially available test device that is easily available at low cost, and shortens the measurement time by sampling only a small number of RF pulses, and the carrier frequency changes with time. A pulse signal with a light frequency can be characterized and used.

[0010]

EXAMPLES A detailed description of the present invention will now be given along with examples. It will be appreciated that the illustrated embodiment is the best mode of the invention. It will be understood that the present invention can adopt other embodiments and is not limited to the configuration according to the drawings.

Referring to FIG. 1, the signal acquisition mechanism of the present invention is shown. The input signal generated by the UUT device is converted to a low frequency pulse stream having an intermediate frequency (IF). The mixer 22 inputs the test signal from the signal source 20 and the control frequency generated by the local oscillator 24,
The IF signal is output as the difference between these frequencies (for example, frequency RF-control frequency = IF). The IF signal is passed through the bandpass filter 26 to remove the unwanted high frequency components. The IF signal is sampled by the digitizer 28 and transferred to the signal processor 30 for frequency analysis. The preferred IF signal frequency is about 20-30% of the digitized sampling frequency. Test signal (that is, IF signal) passed through a down-converter at the selected digitizer sampling frequency
Preferably, at least two cycles of are present in each captured pulse of the test signal. For example, for a 100 nanosecond pulse digitized at 100 megahertz, preferably the IF frequency, the IF frequency will be about 25 megahertz. In this case, 2.5 cycles of the IF signal can be digitized as shown in FIG. Data from 200 pulses are collected sequentially to improve frequency estimation accuracy.

The captured data of FIG. 2 is used as input to the pulse frequency measurement algorithm shown in FIG.
With this configuration, the signal is first interpolated in step 32 by extracting the pulse point and base line data.
The pulse points indicate points within the RF pulse and the baseline points surround the pulse points where no RF signal is present. To remove the DC component from the pulse sine waveform, the baseline is extracted from the pulse point and subtracted, which improves the accuracy of the zero-crossing point. Then, in this configuration, a zero interlace method is applied to the pulse points of the input signal by adding zero points between the extracted points (step 34). The preferred range of interlace ratio is 2-20. The optimum interlace ratio is 4. As an additional function, the forward fast Fourier transform (FF
The frequency analysis method according to T) is applied (step 36), the frequency domain is filtered using a Gaussian filter (step 38), and then the inverse FFT is performed on the filtered frequency domain data (step 40). Is included.

The resulting data is used to interpolate the signal to determine the zero crossing point (step 42). This configuration provides high quality image signal suppression and smooth transient response. Other possible interpolation methods include linear interpolation, Sin (X) X interpolation and polygonal interpolation. The zero-crossing time is used to determine the period of the waveform and this period is used in conjunction with the digitizer sampling rate to calculate the IF frequency (step 44). In this case, it is repeatedly applied to all RF pulses. The final IF frequency measurement is the average of all measurements (step 46), after which non-targets (preferably 1-2 standard deviations) are rejected (step 48). The actual RF frequency is the sum of the measured IF frequency and the control frequency of the local oscillator 24.

In FIG. 4, Sin is directly applied to the captured data.
Another embodiment according to the invention is shown in which the (X) X interpolation method is used to determine the zero-crossing point. The captured data is used as input to the pulse frequency measurement algorithm. In this case, the signal is interpolated (step 46) by first extracting the pulse points and the baseline points. In order to remove the DC component from the pulse sine waveform, the baseline point is extracted from the pulse point and subtracted, which improves the measurement accuracy of the zero-crossing point. The first point before and after each zero crossing point within the time period is then determined (step 48). This time period is then subdivided into sub-regions of 10 points (step 50), Sin (X).
The points before and after the zero-crossing point in the sub-region are obtained by interpolation using the X interpolation method (step 52). The iterative search algorithm determines a zero-crossing point with arbitrary precision between 1/100 and about 1 / 1,000,000 of the digitizer sampling period (step 54). Any time period can be used, but the smaller the time period, the higher the accuracy. Once a point is determined to be within the time period, this point is added to the list of zero-crossing points (step 56). At this time, it can be repeatedly applied to all RF pulses. The zero-crossing number is used to determine the period of the waveform and used in conjunction with the sampling rate to calculate the IF frequency (step 58). The final IF frequency measurement is the average of all measurements (step 60), after which the non-targets (preferably 1-2 standard deviations) are rejected (step 62). The actual RF frequency is the sum of the measured IF frequency and the control frequency of the down-counter local oscillator 24.

[0015]

As described above, according to the present invention, it is understood that the frequency of a narrow pulse width can be measured with a simple structure and the accuracy can be remarkably improved even in a noisy environment in real time. See.

[Brief description of drawings]

FIG. 1 is a block diagram of an RF pulse signal capture procedure.

FIG. 2 is a diagram showing a digitalized sine wave.

FIG. 3 is a flow chart of one embodiment of the present invention.

FIG. 4 is a flow chart of another embodiment of the present invention.

[Explanation of symbols]

 20 Signal Source 22 Mixer 24 Local Oscillator 26 Bandpass Filter 28 Digitizer 30 Signal Processor 32 Baseline Data 34 Pulse Point

 ─────────────────────────────────────────────────── ───Continued from the front page (72) Inventor Elliott Toei Ray Green United States New Jersey 07083, Union, Evergreen Parkway 723

Claims (2)

[Claims] 1. A step of converting an RF pulse into an intermediate pulse stream having an intermediate frequency by taking a difference between a control frequency lower than the frequency of the RF pulse stream and a frequency of the RF pulse stream, and (b) an intermediate step. Digitalizing the pulse flow; (c) extracting pulse points and baseline data from the intermediate pulse flow as samples; (d) subtracting baseline data from each of the pulse points; (e) Determining crossing points using a signal interpolation method on the data obtained in step (d) above;
(F) calculating the period of the intermediate pulse stream signal from the determined zero-crossing point, and (g) calculating the frequency of the intermediate pulse stream signal from the calculated period.
(H) A method of measuring an RF pulse frequency, including the step of adding the calculated intermediate pulse flow frequency and the control frequency to calculate the RF pulse flow frequency. 2. (a) converting the RF pulse into an intermediate pulse flow having an intermediate frequency by taking the difference between the control frequency lower than the frequency of the RF pulse flow and the frequency of the RF pulse flow; and (b) intermediate Digitalizing the pulse flow; (c) extracting pulse points and baseline data from the intermediate pulse flow as samples; (d) subtracting baseline data from each of the pulse points; (e) Find the first point before and after each zero-crossing point in the time period, divide the time period into sub-regions, and then Sin
(X) Iteratively interpolating the first point using the X interpolation method to obtain points before and after the zero-crossing point within the specified accuracy range, and (f) an intermediate pulse flow from the determined zero-crossing point. RF pulse by calculating the period of the signal, (g) calculating the frequency of the intermediate pulse flow signal from the calculated period, and (h) adding the calculated intermediate pulse flow frequency and the control frequency A method of measuring an RF pulse frequency including the step of calculating a flow frequency.